Best Age to Have a Baby

Here's a short summary of Huffington Post's article, What's the Best Age to Have a Baby?.

• In terms of the infant's health, the mother's best age for first-child birth is 26. In terms of the infant's mortality, the best age is 32.
• In terms of the mother's long-term health, the best age is, on average, 31. In terms of the mother's life expectancy, it's 34 or 35.

The primary research article cited by this news report is University of Texas sociologist Dr. John Mirowsky's Parenthood and Health: The Pivotal and Optimal Age at First Birth published in 2002. One other interesting bit in the article is the "positive association between health and age at first birth that is linear for men and parabolic for women". According to the full article (see Fig. 1 on p.333 and confirm with Fig. 2 on p.337), the linearity for men simply means the older, the better. That is, the older the man is at the time his wife or sex partner gives birth to their first baby, the healthier he will be in the future. Note there's an age range for this investigation. Both figures show ages starting at 15 and ending at 45.

Easier to do push-ups in a high flying airplane

A few days ago, I was in an airplane flying at an altitude of over 32,000 feet or 10,000 meters. It was a 13-hour flight. To make this journey a little more comfortable, I did some stretching and, with flight attendants' approval, took a tiny corner to do push-ups. It seems to be easier to do push-ups in this high flying airplane. I did 66 without too much effort, almost tying my record set on ground 20+ years ago.

I'm curious to see how much easier to do this exercise at this altitude. So here's my calculation. If I simplify the calculation by assuming all the mass of the earth to be at the center of the earth (as opposed to integrating the mass along the 6371 km radius), Newtonian universal gravitation between me and the earth is reduced by about 3 thousandths at 10000 meters altitude:

F0 = G (mmemearth)/(6371000)^2

F10k = G (mmemearth)/(6371000+10000)^2

where F₀ is the force between me and the earth when I'm at sea level, and F_10k the force when I'm at 10,000 meters altitude. Calculation of the percent change can omit the constant G and both masses m's:

1/(6371000)^2 - 1/(6371000+10000)^2
----------------------------------- = .00313189770433034782 i.e. 0.313%
        1/(6371000)^2

For a person weighing 70 kg or 154 pounds, that translates to 0.22 kg or about half a pound.

What's more, since the plane travels at the speed of 900 km (560 miles) per hour on this inter-continental flight, the centrifugal force [note] additionally reduces a 70 kg person by 686 newtons or 700 grams:

Fc10k = 70000 * (900000/3600)^2/(6371000+10000) = 685.62921172230057984641 newtons
 or 700 grams or 1.54 pounds

So in total, the body weight is effectively reduced by about 0.5 + 1.5 = 2 pounds in the plane traveling at 900 km/hour at 10000 meters altitude.

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[note] Centrifugal force is imaginary in Newtonian mechanics and is used as a convenient expedient. A physicist may choose to do calculation in Lagrangian mechanics.

Reverseing Alzheimer's disease

Alzheimer's disease is generally believed to be non-curable. But a recent off-purpose finding shows that a cancer treatment drug, saracatinib, can reverse the symptoms of the disease, on rats for now. Read Repurposed experimental cancer drug restores brain function in mouse models of Alzheimer’s disease. Also interesting is that "Individuals interested in participating in the trial can find more information at https://clinicaltrials.gov/ct2/show/NCT02167256?term=Alzheimer+AND+Fyn&rank=2".

Gout may protect against Alzheimer's disease, or not

Articles like Gout May Protect Against Alzheimer's Disease have been around for quite some time. Indeed there's plenty of evidence for the protective effect of gout, or rather, uric acid, on Alzheimer's disease. I just want to point out that there does exist conflicting evidence from other researches, such as this 2-page report, No association between gout and Alzheimer's disease: results of a case–control study in older people in Taiwan(Int J Geriatr Psychiatry 2013; 28: 1205-1206). In case you can't read it, here's one passage (emphasis added):

Both studies [in Italy and Portugal] have conveyed the message that high level of uric acid may increase the risk of Alzheimer's disease. In this present study, we found that no association is detected between gout and Alzheimer's disease in both gender, whether gouty patients had ever used urate-lowering drugs or not. Because conflicting results exist, further studies are required to confirm the association between gout and Alzheimer's disease.

Tooth brushing

Some tips:

1. You're supposed to brush your teeth for at least 2 minutes. But if you really don't have the patience, try brushing more on the trouble spots and less on the good teeth. Usually the molars need more of your attention. So repeatedly brush those, in both left-and-right, and back-and-forth directions, inside and outside. Given the same total brushing time, you've made best use of your time.

2. Tongue cleaning is healthful because it clears out germs and eliminates or reduces bad breath, but it's not commonly practiced. Instead of using special tools, why not just use your tooth brushes on the surface of your tongue, or even below it? A few seconds of doing it doesn't take long and brings great benefit.

3. Not really tooth brushing. But I find that the easiest way to remove stains on teeth, such as those left by coffee or tea, is, surprisingly, rubbing with a white rubber eraser! Try it. It works. No need to research for side effects, because there is none. The only problem is that it only works on the teeth in the front, incisors and maybe canines, and not even the inner side of them, and the effect is obviously not as dramatic as the real solution, which may shock your friends and coworkers by suddenly showing ghastly white teeth. Isn't it more pleasing to have just slightly whiter teeth than before? And you only show the front teeth to people you're facing anyway.